Integrin but not CEACAM receptors are dispensable for Helicobacter pylori CagA translocation

Abstract

Translocation of the Helicobacter pylori (Hp) cytotoxin-associated gene A (CagA) effector protein via the cag-Type IV Secretion System (cag-T4SS) into host cells is a hallmark of infection with Hp and a major risk factor for severe gastric diseases, including gastric cancer. To mediate the injection of CagA, Hp uses a membrane-embedded syringe-like molecular apparatus extended by an external pilus-like rod structure that binds host cell surface integrin heterodimers. It is still largely unclear how the interaction of the cag-T4SS finally mediates translocation of the CagA protein into the cell cytoplasm. Recently certain carcinoembryonic antigen-related cell adhesion molecules (CEACAMs), acting as receptor for the Hp outer membrane adhesin HopQ, have been identified to be involved in the process of CagA host cell injection. Here, we applied the CRISPR/Cas9-knockout technology to generate defined human gastric AGS and KatoIII integrin knockout cell lines. Although confocal laser scanning microscopy revealed a co-localization of Hp and β1 integrin heterodimers on gastric epithelial cells, Hp infection studies using the quantitative and highly sensitive Hp β-lactamase reporter system clearly show that neither β1 integrin heterodimers (α1β1, α2β1 or α5β1), nor any other αβ integrin heterodimers on the cell surface are essential for CagA translocation. In contrast, deletion of the HopQ adhesin in Hp, or the simultaneous knockout of the receptors CEACAM1, CEACAM5 and CEACAM6 in KatoIII cells abolished CagA injection nearly completely, although bacterial binding was only reduced to 50%. These data provide genetic evidence that the cag-T4SS-mediated interaction of Hp with cell surface integrins on human gastric epithelial cells is not essential for CagA translocation, but interaction of Hp with CEACAM receptors is facilitating CagA translocation by the cag-T4SS of this important microbe.

Specific high affinity interaction of Helicobacter pylori CagL with integrin αVβ6 promotes type IV secretion of CagA into human cells

“…C,D). The expression of CEACAM1 combined with the susceptibility for CagA translocation in SW480 cells is consistent with the finding that CEACAMs play a role in CagA translocation . Zhao et al .…”

“…At the protein level, Zhao et al . found about 4.5‐fold increased expression of the HopQ receptor CEACEAM1 in integrin‐deficient Kato III cells. As a result, wildtype H. pylori showed increased adhesion to integrin‐deficient Kato III cells.…”

“…The gastric epithelial cell line AGS is arguably the most common model system to study H. pylori infection in vitro . AGS cells express integrin α V β 6 in addition to α 5 β 1 and α V β 5 , but show no expression of α V β 3 and α V β 8 . To investigate whether integrin α V β 6 may function as host cell receptor for the cag T4SS in AGS cells, we analysed the α V β 6 dependency of the CagA translocation using the anti‐α V β 6 function‐blocking antibody 3G9 .…”

Review: Pathogenesis of Helicobacter pylori infection

“…24 Recently, certain carcinoembryonic antigen-related cell adhesion molecules (CECAMs), which capture H pylori outer membrane adhesin HopQ, were found to participate in CagA translocation.…”

“…However, deletion of the HopQ or simultaneous deletion of CEACAM1, CEACAM5, and CEACAM6 in Kato III cells totally blocked translocation of CagA 24. Neither β1 integrin heterodimers (α1β1, α2β2, α5β1) nor any other αβ integrin heterodimers on the cell surface were involved in CagA translocation.…”